powerpc: Fix up implicit stat.h users

They get it via module.h (via device.h) but we want to clean that up.
When we do, we'll get things like:

ibmebus.c:314: error: 'S_IWUSR' undeclared here (not in a function)
vio.c:972: error: 'S_IWUSR' undeclared here (not in a function)

so add in the stat header it is using explicitly in advance.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index 3e7f651..029a562 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -12,6 +12,7 @@
 #include <linux/kernel.h>
 #include <linux/kobject.h>
 #include <linux/smp.h>
+#include <linux/stat.h>
 #include <linux/completion.h>
 #include <linux/device.h>
 #include <linux/delay.h>